1. Field of the Invention
The present invention relates to a gas removal method, a gas removal system and a plasma processing apparatus that are ideal in applications in which plasma processing is executed with a gas containing halogen (a halogen gas).
2. Description of the Related Art
Plasma processing apparatuses that execute plasma processing by using a halogen gas such as a chlorine-based gas are utilized in the field of semiconductor production in the related art. During an etching process executed by using a chlorine-based gas, a chlorine-based reaction product becomes deposited at the inner wall surfaces of the processing chamber and internal members constituting the processing apparatus and the etching process is adversely affected by the chlorine-based reaction product deposit. For this reason, it is necessary to regularly clean the inside of the processing chamber with an organic solvent such as alcohol. However, the chlorine-based gas, as well as the chlorine-based reaction product, is present inside the processing chamber immediately after the process and it is dangerous to open the processing chamber in such a state.
Accordingly, the chlorine-based gas is removed while maintaining the processing chamber in an airtight state in the related art. When the atmospheric air and N2 are supplied into the processing chamber in a sealed state, the chlorine-based gas is transformed to acid by the moisture contained in the atmospheric air. By evacuating this acid through an acid evacuation line, the chlorine-based gas is removed from the processing chamber. Only after the chlorine-based gas is removed as described above and safety is thus assured, the processing chamber is opened to the atmosphere for cleaning.
However, since the atmospheric air and N2 are supplied into the sealed processing chamber, there is a limit to the quantities of atmospheric air and N2 that can be taken in and it takes a considerable length of time to supply the atmospheric air and N2 and to transform the chlorine-based gas to acid in the related art described above. It takes as long as approximately 300 minutes to lower the chlorine-based gas concentration to the level at which the processing chamber can be safely opened, i.e., under 2 ppm, in a standard plasma processing apparatus, to lead to an increase in the down time of the apparatus and a poor operating rate.